1. Field of the Invention
This invention relates to a method of manufacturing a capacitor in a semiconductor device. In particular, it relates to a method of manufacturing a capacitor in a semiconductor device that can improve the electric characteristic of the capacitor by forming a ferroelectric thin film that has an orientation polarization structure so that the endurance limit is enhanced and the aging of the ferroelectric thin film is improved.
2. Description of the Related Prior Art
Generally, ferroelectric material such as (Pb, Zr)TiO.sub.3 (hereinafter, referred to as a PZT) has hundreds to thousands of a dielectric constant at room temperature and has bistable remanent polarization. A nonvolatile memory device can be obtained by forming the ferroelectric material in the form of a thin film.
The nonvolatile memory device formed by the ferroelectric thin film utilizes the principle that a signal is input thereon by controlling polarization direction according to the direction of the applied electric field and digital signals 1 and 0 are stored thereon in response to direction of the remanent polarization when the electric field is removed.
In a method of manufacturing the ferroelectric thin film such as a PZT, a physical vapor deposition method is more widely used than a chemical vapor deposition method since the physical vapor deposition method is interchangeable with a conventional semiconductor process and can produce a reliable device having a good quality in contrast to the chemical vapor deposition method.
In the physical vapor deposition method, the radio frequency (RF) plasma sputtering method is mainly used.
However, use of the ferroelectric thin film has been delayed in application of a memory device due to deterioration of the ferroelectric thin film. This means a default such as an oxygen void which is space charge exists in the thin film. Such a default is moved to a grain boundary or domain wall, thereby forming a space charge layer. The space charge layer forms an electric field in the opposite direction of a self polarization, resulting in decreased polarization.
That is, such a ferroelectric thin film has a polybound and has an irregular domain wall. When the direction of the polarization is changed by application of an electric field, the default bipolar has a direction which is different from the polarization direction which induced a reverse bias. Also, the default bipolar disturbs movement of the domain wall and the dielectric characteristic is deteriorated. Hence, there is a problem in that the ferroelectric thin film has been delayed in the application to a memory device.